1. Field of the Invention
The present invention relates to rotary compressors for refrigeration systems, and more particularly, to a variable capacity rotary compressor having a variable compressing capacity.
2. Description of the Related Art
Generally, refrigerating systems, such as air conditioners or refrigerators, use variable capacity rotary compressors, a refrigerant compressing capacity of which is varied as desired to vary the refrigerating capacity of the systems.
FIG. 1 shows a sectional view of a conventional variable capacity rotary compressor disclosed in U.S. Pat. No. 5,871,342. As shown in FIG. 1, the conventional variable capacity rotary compressor comprises a housing 1, with a cylindrical compressing chamber 2 defined in the housing 1 and a ring piston 3 installed in the cylindrical compressing chamber 2 so as to have the ring piston 3 eccentrically rotate in the cylindrical compressing chamber 2. A plurality of outer vanes 4 are slidably mounted in the housing 1 so as to have the outer vanes 4 be retractable in radial directions while being in contact with the outer surface of the ring piston 3. That is, the outer vanes 4 divide the cylindrical compressing chamber 2 of the housing 1 into a plurality of variable gas chambers 2a and 2b. 
A plurality of vane deactivation assemblies 5 are installed on the housing 1 at corresponding positions adjacent to the outer vanes 4 to deactivate the outer vanes 4 or release the outer vanes 4 from a deactivated state. Each of the vane deactivation assemblies 5 includes a deactivation pin 5b which engages a deactivation recess 4a in its respective outer vane 4 in response to a corresponding one or both solenoid actuators 5a being energized. The deactivation pins 5b hold the outer vanes 4 in a retracted position out of contact with the ring piston 3, thus deactivating the outer vanes 4 and reducing the capacity of the variable capacity rotary compressor. The variable capacity of the variable capacity rotary compressor is thus accomplished.
However, the above variable capacity rotary compressor is problematic in that the vane deactivation assemblies 5 have a complex construction. That is, the vane deactivation assemblies 5 are designed such that the deactivation pins 5b of the deactivation assemblies 5 selectively deactivate the outer vanes 4 while advancing or retracting in radial directions by the solenoid actuators 5a installed on the housing 1. Due to such a complex construction, producing the above variable capacity rotary compressor is difficult and the production cost of the variable capacity rotary compressor is high.
Accordingly, an aspect of the present invention is to provide a variable capacity rotary compressor which has a simple construction, easily varies its refrigerant compressing capacity, as desired, and is easy to produce at a low production cost.
To achieve the above and/or other aspects of the present invention, there is provided a variable capacity rotary compressor, comprising a housing having a cylindrical compressing chamber defined in the housing, a rotating shaft having an eccentric body part which rotates in the compressing chamber of the housing, a ring piston which is fitted over the eccentric body part of the rotating shaft and rotates while being in contact with an inner surface of the compressing chamber a vane which is mounted in the housing and advances or retracts in a radial direction of the compressing chamber in accordance with a rotation of the ring piston, and a control unit which is connected to the vane and controls a moving range of the vane by moving in opposite directions in response to pressures of a refrigerant inlet and a refrigerant outlet of the compressor.
The control unit may comprise a control cylinder having a control piston and mounted outside the housing, wherein the control piston is set in the control cylinder so as to advance and retract in the same direction as a moving direction of the vane, a connecting member which connects the vane to the control piston so as to push or pull the vane in response to a movement of the control piston, a first control path which communicates with an interior of the control cylinder, a second control path which allows the first control path to communicate with the refrigerant outlet of the compressor, a third control path which allows the first control path to communicate with the refrigerant inlet of the compressor, and a path control valve installed at a confluence of the first, second and third control paths.
The path control valve may be a three-way valve which selectively allows the first control path to communicate with one of the second and third control paths.
In the rotary compressor, the vane may come into contact at an end thereof with a portion of an outer surface of the ring piston at which a radius of a rotation of the ring piston is at a maximum, in response to the first control path communicating with the second control path and allowing the pressure of the refrigerant outlet of the compressor to act on the control piston. The vane may be spaced apart from the portion of the outer surface of the ring piston at which the radius of the rotation of the ring piston is at a minimum, in response to the first control path communicating with the third control path and allowing the pressure of the refrigerant inlet of the compressor to act on the control piston.
The control unit may further comprise a first spring which normally biases the vane toward the ring piston, and a second spring which normally biases the ring piston in a direction opposite to a direction in which the first spring biases the vane. The second spring may have a higher elasticity than that of the first spring.
The variable capacity rotary compressor may further comprise a hermetic casing, wherein the housing is set in the hermetic casing, the control piston is set in the control cylinder, which is mounted to an outer surface of the hermetic casing, and the connecting member penetrates the hermetic casing so as to connect the vane to the control piston.